A mutation in the Arabidopsis gene STARIK leads to dwarfism and chlorosis of plants with an altered morphology of leaf and cell nuclei. We show that the STARIK gene encodes the mitochondrial ABC transporter Sta1 that belongs to a subfamily of Arabidopsis half-ABC transporters. The severity of the starik phenotype is suppressed by the ectopic exp...

A mutation in the Arabidopsis gene STARIK leads to dwarfism and chlorosis of plants with an altered morphology of leaf and cell nuclei. We show that the STARIK gene encodes the mitochondrial ABC transporter Sta1 that belongs to a subfamily of Arabidopsis half-ABC transporters. The severity of the starik phenotype is suppressed by the ectopic expression of the STA2 homolog; thus, Sta1 function is partially redundant. Sta1 supports the maturation of cytosolic Fe/S protein in �atm1 yeast, substituting for the ABC transporter Atm1p. Similar to Atm1p-deficient yeast, mitochondria of the starik mutant accumulated more nonheme, nonprotein iron than did wild-type organelles. We further show that plant mitochondria contain a putative L-cysteine desulfurase. Taken together, our results suggest that plant mitochondria possess an evolutionarily conserved Fe/S cluster biosynthesis pathway, which is linked to the intracellular iron homeostasis by the function of Atm1p-like ABC transporters. Minimize

A mutation in the Arabidopsis gene STARIK leads to dwarfism and chlorosis of plants with an altered morphology of leaf and cell nuclei. We show that the STARIK gene encodes the mitochondrial ABC transporter Sta1 that belongs to a subfamily of Arabidopsis half-ABC transporters. The severity of the starik phenotype is suppressed by the ectopic exp...

A mutation in the Arabidopsis gene STARIK leads to dwarfism and chlorosis of plants with an altered morphology of leaf and cell nuclei. We show that the STARIK gene encodes the mitochondrial ABC transporter Sta1 that belongs to a subfamily of Arabidopsis half-ABC transporters. The severity of the starik phenotype is suppressed by the ectopic expression of the STA2 homolog; thus, Sta1 function is partially redundant. Sta1 supports the maturation of cytosolic Fe/S protein in �atm1 yeast, substituting for the ABC transporter Atm1p. Similar to Atm1p-deficient yeast, mitochondria of the starik mutant accumulated more nonheme, nonprotein iron than did wild-type organelles. We further show that plant mitochondria contain a putative L-cysteine desulfurase. Taken together, our results suggest that plant mitochondria possess an evolutionarily conserved Fe/S cluster biosynthesis pathway, which is linked to the intracellular iron homeostasis by the function of Atm1p-like ABC transporters. Minimize

Iron-sulfur (Fe/S) cluster-containing proteins catalyze a number of electron transfer and metabolic reactions. The components and molecular mechanisms involved in the assembly of the Fe/S clusters have been identified only partially. In eukaryotes, mitochondria have been proposed to execute a crucial task in the generation of intramitochondrial ...

Iron-sulfur (Fe/S) cluster-containing proteins catalyze a number of electron transfer and metabolic reactions. The components and molecular mechanisms involved in the assembly of the Fe/S clusters have been identified only partially. In eukaryotes, mitochondria have been proposed to execute a crucial task in the generation of intramitochondrial and extramitochondrial Fe/S proteins. Herein, we identify the essential ferredoxin Yah1p of Saccharomyces cerevisiae mitochondria as a central component of the Fe/S protein biosynthesis machinery. Depletion of Yah1p by regulated gene expression resulted in a 30-fold accumulation of iron within mitochondria, similar to what has been reported for other components involved in Fe/S protein biogenesis. Yah1p was shown to be required for the assembly of Fe/S proteins both inside mitochondria and in the cytosol. Apparently, at least one of the steps of Fe/S cluster biogenesis within mitochondria requires reduction by ferredoxin. Our findings lend support to the idea of a primary function of mitochondria in the biosynthesis of Fe/S proteins outside the organelle. To our knowledge, Yah1p is the first member of the ferredoxin family for which a function in Fe/S cluster formation has been established. A similar role may be predicted for the bacterial homologs that are encoded within iron-sulfur cluster assembly (isc) operons of prokaryotes. Minimize

Import of most nucleus-encoded preproteins into mitochondria is mediated by N-terminal presequences and requires a membrane potential and ATP hydrolysis. Little is known about the chemical nature and localization of other mitochondrial targeting signals or of the mechanisms by which they facilitate membrane passage. Mitochondrial heme lyases lac...

Import of most nucleus-encoded preproteins into mitochondria is mediated by N-terminal presequences and requires a membrane potential and ATP hydrolysis. Little is known about the chemical nature and localization of other mitochondrial targeting signals or of the mechanisms by which they facilitate membrane passage. Mitochondrial heme lyases lack N-terminal targeting information. These proteins are localized in the intermembrane space and are essential for the covalent attachment of heme to c type cytochromes. For import of heme lyases, the translocase of the mitochondrial outer membrane complex is both necessary and sufficient. Here, we report the identification of the targeting signal of mitochondrial heme lyases in the third quarter of these proteins. The targeting sequence is highly conserved among all known heme lyases. Its chemical character is hydrophilic because of a large fraction of both positively and negatively charged amino acid residues. These features clearly distinguish this signal from classical presequences. When inserted into a cytosolic protein, the targeting sequence directs the fusion protein into the intermembrane space, even in the absence of a membrane potential or ATP hydrolysis. The heme lyase targeting sequence represents the first topogenic signal for energy-independent transport into the intermembrane space and harbors two types of information. It assures accurate recognition and translocation by the translocase of the mitochondrial outer membrane complex, and it is responsible for driving the import reaction by undergoing high-affinity interactions with components of the intermembrane space. Minimize